Ultrasonic transmission devices are frequently used in a variety of applications, such as surgical operations and procedures. Typically, these transmission devices usually include a transducer that converts electrical energy into vibrational motion at ultrasonic frequencies. The vibrational motion is usually transmitted through a transmission component, such as a mounting device, to vibrate a distal end of another transmission component, such as a working member.
The working member is usually attached to the mounting device by a threaded joint. In particular, the proximal end of the working member typically includes a threaded stud that is threaded into a threaded bore of the distal end of the mounting device. The tension between the threaded stud of the working member and the threaded bore of the mounting device provides an axial compression force to prevent the working member and mounting device from separating. However, the threaded bore and the threaded stud are usually costly to fabricate and are typically required to be manufactured within specific tolerance ranges. In addition, it can be difficult to manufacture threaded bores and threaded studs with small diameters.
The working member is usually tightened to the mounting device by using a tool, such a wrench. However, the use of as a wrench may cause the working member to be inadvertently over-tightened, which may tend to strip or damage the threads of the working member and mounting device. When the working member is over-tightened, the working member may be difficult to detach from the mounting device. On the other hand, insufficient tightening of the working member to the mounting device may cause undesired heat build-up of the threaded joints, decrease the transfer of energy across the junction, and cause unwanted transverse motion.
A torque limiting device may also be used to tighten the working member to the mounting device. The torque limiting device is used to assure that a predetermined minimum torque is reached and that a maximum torque is not exceeded when tightening the working member to the mounting device. In one known technique, a separate torque wrench W as illustrated in FIG. 1 may be placed over a working member WM to tighten and untighten the working member WM from a mounting device M of a surgical device. In this technique, the working member WM is attached to the mounting device M by a threaded connection. Once the working member WM is threaded onto the mounting device M, the torque wrench W is then slipped over the working member WM to tighten the working member WM to the mounting device M. A nose cone is then threaded onto the distal end of the handpiece assembly H.
However, it is quite difficult for a user to connect and disconnect the working member from the mounting device in a sterile field when using a separate torque wrench. Further, it may be cumbersome and time consuming to use a torque wrench when changing the working member during an operation or for tightening certain working members to the mounting device. Additionally, the torque wrench can be mislaid or lost and may require calibration or replacement at frequent intervals to ensure accuracy.
Accordingly, there is a need for improved devices and methods to join ultrasonic transmission components. Such devices would further benefit if the transmission components could be readily attached and detached without the use of a separate torque limiting device.